Preston, who got his title after working on the 'Let It Be' and 'Abbey Road' albums, had been in a coma since November battling kidney failure and passed away in Phoenix, Arizona.
The songwriter and keyboard player also worked with the Rolling Stones, Ray Charles and Little Richard.
Since his death tributes have been pouring in from various music legends who knew Preston.
Rolling Stones frontman Mick Jagger said: "Billy was a fantastic and gifted musician. He was great fun to be with and I will miss him a lot." Sir Elton John said that Preston had been a musical inspiration and "one of the greatest keyboard players of all time".
In the 70s, Preston topped the charts as a solo act winning a Grammy award for his 'Outa Space' instrumental and also wrote Joe Cocker's 1974 hit 'You Are So Beautiful'.
Preston - who played on both sides of the 'Get Back/Don't Let Me Down' single - became the only musician to get a co-credit on a Beatles record.
In recent years, even when his health deteriorated as a result of past drug use, he worked with the Red Hot Chili Peppers and Neil Diamond.